Don Carlo was all brains, but he wasn't all that tough. A lot of the blue collar hoodlums in his family were embarrassed to have him as a boss. He was much more of a businessman than a Cosa Nostra boss. I don't think he would've ever become boss if it hadn't been for his powerful friends.

And no The Colombos were never ever a sub group of the Gambinos. Not even close. You think guys like Carmine Persico or Sonny Franzese would ever let a guy like Carlo Gambino boss them around? Or Crazy Joe, a guy who went to war with his own boss!! Not too mention the fact that Crazy Joe beat Neil Dellacroce to a bloody pulp inside a crowded New York restaurant in the early 1960s.